which is easier experimentally. This measurement was pioneered by the HERMES collaboration [1]}. A drawback, however, is that it depends non-linearly on the DVCS amplitudes because of the denominator.
One can further project the beam charge asymmetry on the various harmonics:
\(A_C^{\cos {(n\phi )}}=\frac{2-\delta _{n0}}{2\pi }\int ^\pi _{-\pi } d\phi _{\gamma \gamma }\cos {(n\phi _{\gamma \gamma })}A_C(\phi _{\gamma \gamma })\,,\) 
